A COMPARATIVE-ANALYSIS OF 2ND-TRIMESTER ULTRASOUND DATING FORMULAS INPREGNANCIES CONCEIVED WITH ARTIFICIAL REPRODUCTIVE TECHNIQUES

A dataset of 64 pregnancies conceived by artificial reproductive techn iques was studied to assess the accuracy of second-trimester dating fo rmulae when these were applied in routine ultrasound clinics in differ ent centers. Dating formulae for biparietal diameter (BPD) and femur l ength (FL) were derived for a gestational age range of 14-23 weeks. Th e best fit curves represented linear equations: gestational age (days) = 44.2 + 2 x BPD; and gestational age (days) = 67.4 + 2.3 x FL. Twelv e published formulae for biparietal diameter and femur length were rev iewed and systematic and random errors were calculated for these formu lae when they were applied to second-trimester scan measurements in pr ecisely dated pregnancies. Overall, published dating formulae performe d well in Predicting gestational age. The 95% confidence interval was 8.3 days for biparietal diameter and 10.2 days for femur length. The s tudy confirms the accuracy of ultrasound dating in routine ultrasound clinics and supports the use of ultrasound measurement alone in prefer ence to menstrual history for dating pregnancy.